Constraining the alkenone unsaturation index

Bonnie Loren Epstein, University of Rhode Island


The variability of climate in the recent geologic past is often considered a useful guide to the potential scale and consequences of future climate change. Alkenones, 37-carbon methyl ketones with two, three or four double bonds produced primarily by the ubiquitous coccolithophorid algae Emiliania huxleyi , have become popular paleothermometers. Alkenones are related to sea surface temperature through the alkenone unsaturation index, UK 37 . ^ At the time our study took place, it was the first to specifically examine non-thermal variation of UK 37 values of E. huxleyi. We found that E. huxleyi strains vary their UK 37 values at constant temperature, but in a manner dissimilar to each other. The factors which cause alkenone ratios to vary in living cells likely depends on the function they serve in the cell. This thesis provides some positive evidence that alkenones are not membrane lipids, as had popularly been assumed, but metabolic storage molecules. The work in this thesis indicates that alkenone unsaturation ratios are not appropriate for many of the small temperature changes for which they have previously been used. Our results also suggest that alkenones in sediment may be primarily derived from cells in stationary phase. ^

Subject Area

Biogeochemistry|Paleoecology|Environmental Sciences

Recommended Citation

Bonnie Loren Epstein, "Constraining the alkenone unsaturation index" (1999). Dissertations and Master's Theses (Campus Access). Paper AAI9960022.